---
title: Introduction
description: HexKit is a browser toolkit for decoding, simulating and debugging Vara program messages and EVM transactions.
url: http://hexdocs.thally.app/
lastUpdated: 2026-10-28
lastVerified: 2026-10-28T00:00:00.000Z
---

# Introduction

HexKit is a browser toolkit for decoding, simulating and debugging Vara program messages and EVM transactions.

HexKit shows you what a smart-contract call did, or what it would do, in plain names instead of hex. It runs in your browser at [hexkit.app](https://hexkit.app). There is nothing to install and no account to create.

These docs cover HexKit's Vara tools, added in October 2026.

## Who it's for

- Developers building [Sails](https://wiki.vara.network/docs/build/sails) programs on Vara who need to know why a message succeeded, failed, or would fail if sent again.
- Auditors and support engineers reading someone else's messages without the program's source.
- Anyone who needs a decoded record of a message that they can save and share.

## What it does on Vara

| Tool | Use it to |
| --- | --- |
| Message Inspector | Decode a sent message: its call, reply, events and dispatch status. HexKit fetches the program's interface (IDL) for you. |
| Message Simulation | Calculate a message's reply at a chosen block without signing anything. |
| Program Interaction | Load a program by ID and query it through forms built from its Sails IDL. |
| Scenario Tests | Run a program's WASM against a local test runtime and assert replies across several messages. |
| IDL Comparison | Compare two versions of a Sails interface and check saved payloads against both. |
| Event Explorer | Decode a program's Sails events over a block range and export them. |
| Vara.eth Settlement | Match Mirror requests to their replies by message ID and check Ethereum finality. |

HexKit's EVM tools sit behind the **EVM** switch at the top left of the app. These docs don't cover them yet.

  <img src="/images/vara-tools-nav.png" alt="HexKit header with the EVM and Vara switch at the top left, and the Programs & messages, Utilities and Vara.eth tool groups" />

## What you need

- A desktop browser.
- A Polkadot-compatible wallet extension, but only to send a message. Reading, decoding and dry runs work without one.

#### [Quickstart](/quickstart)

Decode a real mainnet message.

#### [Replay a message at two blocks](/guides/replay-a-message)

Find out whether a message would still succeed today, and why.